Apollo 14: V47 vs. V66 After CSM S.V. Uplink?

Wedge313

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Hi,

Just completed MCC-6 on my way back to earth, and I have a question...

Earlier in the flight after uplinking the CSM S.V. they did a V66 to set it into the LM slot. Now after the CSM S.V. uplink they have us doing a V47 to set the LM S.V. into the CSM slot. Why the difference? Is it accomplishing basically the same thing?

Thanks
 

indy91

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Hmm I don't know exactly why the procedure is as written in the flight plan, but it was to preserve the CMC state vector. Ever since TEI the onboard state vector was mostly left alone and only updated with P23s, to simulate a no-comm situation where it's all on the CMP and P23 to navigate. When it came to the midcourse corrections they still wanted to use the most accurate state vector available, which is the one from ground tracking (MSFN). So they downlinked the current CMC state vector, uplinked the MSFN state vector before the MCC. Executed the MCC and then afterwards they put in the CMC state vector plus maneuver DV back into the CSM slot, and the good MSFN state vector in the LM slot.

But I am not quite sure what all the V47s are for. There is a mention about this in the FIDO report, but it only gives a suggested procedure to avoid V47s for the next mission and not what/how they did it on Apollo 14 sadly. Maybe it's something to do with the W-Matrix or onboard state vector propagation, but I can't really find much about this.
 
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